None of the information I asked for suggests that there remains any problem. Neither can I reproduce using the same GPU, whether with Nouveau DDX or Modesetting DIX display driver:
# pinxi -GISaz
System:
Kernel: 5.3.18-150300.59.63-default arch: x86_64 bits: 64 compiler: gcc
v: 7.5.0 parameters: root=LABEL=<filter> ipv6.disable=1 net.ifnames=0
noresume mitigations=auto consoleblank=0
Desktop: KDE v: 3.5.10 tk: Qt v: 3.3.8c info: kicker wm: kwin vt: 7
dm: KDM Distro: openSUSE **Leap 15.3**
Graphics:
**Device**-1: **NVIDIA GT218 [GeForce 210]** vendor: eVga.com. **driver: nouveau**
v: kernel pcie: gen: 1 speed: 2.5 GT/s lanes: 16 ports:
active: DVI-I-1,VGA-1 empty: HDMI-A-1 bus-ID: 01:00.0 chip-ID: 10de:0a65
class-ID: 0300
**Display**: x11 server: **X.Org v: 1.20.3 driver: X: loaded: nouveau**
unloaded: fbdev,modesetting,vesa alternate: nv,nvidia gpu: nouveau
display-ID: :0 screens: 1
**Screen**-1: 0 s-res: **4480x1440** s-dpi: 120 s-size: 948x304mm (37.32x11.97")
s-diag: 996mm (39.19")
Monitor-1: DVI-I-1 pos: primary,left model: Acer K272HUL serial: <filter>
built: 2018 res: 2560x1440 hz: 60 dpi: 109 gamma: 1.2
size: 598x336mm (23.54x13.23") diag: 686mm (27") ratio: 16:9 modes:
max: 2560x1440 min: 720x400
**Monitor-2**: **VGA-1** pos: right model: Samsung built: 2009 **res: 1920x1080**
hz: 60 dpi: 55 gamma: 1.2 size: 886x498mm (34.88x19.61")
diag: 1012mm (39.8") **ratio: 16:9** modes: max: 1920x1080 min: 720x400
OpenGL: renderer: NVA8 v: 3.3 Mesa 20.2.4 direct render: Yes
Info:...Shell: Bash v: 4.4.23 running-in: konsole pinxi: 3.3.15-5
# pinxi -GISaz
System:
Kernel: 5.3.18-150300.59.63-default arch: x86_64 bits: 64 compiler: gcc
v: 7.5.0 parameters: root=LABEL=<filter> ipv6.disable=1 net.ifnames=0
noresume mitigations=auto consoleblank=0
Desktop: KDE v: 3.5.10 tk: Qt v: 3.3.8c info: kicker wm: kwin vt: 7
dm: KDM Distro: openSUSE **Leap 15.3**
Graphics:
**Device**-1: **NVIDIA GT218 [GeForce 210]** vendor: eVga.com. **driver: nouveau**
v: kernel pcie: gen: 1 speed: 2.5 GT/s lanes: 16 ports:
active: DVI-I-1,VGA-1 empty: HDMI-A-1 bus-ID: 01:00.0 chip-ID: 10de:0a65
class-ID: 0300
**Display**: x11 server: **X.Org v: 1.20.3 driver: X: loaded: modesetting**
gpu: nouveau display-ID: :0 screens: 1
**Screen**-1: 0 s-res: **4480x1440** s-dpi: 120 s-size: 948x304mm (37.32x11.97")
s-diag: 996mm (39.19")
Monitor-1: DVI-I-1 pos: primary,left model: Acer K272HUL serial: <filter>
built: 2018 res: 2560x1440 hz: 60 dpi: 109 gamma: 1.2
size: 598x336mm (23.54x13.23") diag: 686mm (27") ratio: 16:9 modes:
max: 2560x1440 min: 720x400
**Monitor-2: VGA-1** pos: right model: Samsung built: 2009 **res: 1920x1080**
hz: 60 dpi: 55 gamma: 1.2 size: 886x498mm (34.88x19.61")
diag: 1012mm (39.8") **ratio: 16:9** modes: max: 1920x1080 min: 720x400
OpenGL: renderer: NVA8 v: 3.3 Mesa 20.2.4 direct render: Yes
Info:...Shell: Bash v: 4.4.23 running-in: konsole pinxi: 3.3.15-5
With both Xorg display drivers, the 1920x1080 display connected to my VGA GPU output is working automagically at the correct 16:9 ratio.
Has your problem disappeared? If not, try at your login screen selecting a desktop session other than XFCE, such as IceWM, which is light weight (3 packages, if not already installed, Installed Size : 963.1 KiB for the main one) and should not be reusing any of your XFCE session settings. This should confirm or rule out XFCE and/or your XFCE settings as the problem source. If this eliminates the trouble, try creating a new user to see how XFCE works with default settings.
I suppose LightDM could have something to do with this, though I doubt it. You can switch to another DM using:
sudo update-alternatives --config default-displaymanager
Also, paste here output from the following:
ls -l /etc/X11/ /etc/X11/xorg.conf.d/
grep ouveau /etc/X11/xorg.conf.d/*conf
Before using inxi again, please run sudo inxi -U. The version in Leap is a broken antique. -U updates it to the latest version from upstream. (The pinxi I used above is the latest devel version of inxi.)